Composite coreboard having a plurality of partially nested,channel-shaped skin elements



y 7, 1910 c. J. RODMAN ETAL 3,519,523

COMPOSITE COREBOARD HAVING A PLURALITY OF PARTIALLY NESTED, CHANNEL-SHAPED SKIN ELEMENTS 2 Sheets-Sheet 1 Filed Dec. 4, 1.967

m 8 MN E E W 0 R J B EK ms EN MW L H CT ATTORNEYS July 7, 1970 c, J, RODMAN ETAL 3,519,523

COMPOSITE COREBOARD HAVING A PLURALITY OF PARTIALLY NESTED, CHANNEL-SHAPED SKIN ELEMENTS Filed Dec. 4, 1.967 2 Sheets-Sheet 2 ma 0 w MN I A E E f flflnfln. nflnflfll l VMM ND 0 l n 6 I J F EK ms EN RR A0 LH CT FIG. 7

ATTORNEYS United States Patent COMPOSITE COREBOARD HAVING A PLURALITY 0F PARTIALLY NESTED, CHANNEL-SHAPED SKIN ELEMENTS Clarence J. Rodman and Theme K. Broome, Alliance,

Ohio, assignors of one-half each to said Rodman, d0- ing business as Alliance Tool Company, Alliance, Ohio, and said Broome Filed Dec. 4, 1967, Ser. No. 687,571 Int. Cl. B32b 3/14 U.S. Cl. 161-36 7 Claims ABSTRACT OF THE DISCLOSURE A skin element having an improved septum for use in composite coreboard construction. The skin element is generally of channel-shaped cross section with the sep tum, or web portion, oriented transversely of the substantially parallel, spaced flanged portions. The septum is provided with a plurality of longitudinally spaced, lateral offsets which increase its columnar strength. This increase in columnar strength provides a greater bending strength to the coreboard. In addition, passages through the septum are positioned so as not to diminish the increased columnar strength thereof. When assembled in a coreboard, the skin elements are partially nested toform longitudinal cells between the spaced septums of successive skin elements. The core, a rigid, but frangible, cellular foam, fills these cells. The aforesaid passages eliminate distortion to the septums that would reduce their columnar strength by permitting communication between the cells as the core forms. These passages also provide a mechanical bond for the core material between successive cells after the core is formed, and this bond further tends to stabilize the desired orientation of the septums transversely of the board.

BACKGROUND OF THE INVENTION The present invention relates generally to a skin element having a septum of high columnar strength for use in composite coreboard, the increased columnar strength of the septum providing an increased bending strength to the coreboard.

Coreboard is acquiring an ever increasing popularity in the building and construction industry. A coreboard comprises a combination of two ingredients: a core and a reinforcement. The core is generally a cellular plastic, such as foamed polystyrene, foamed cellulose acetate, or the like, which is light in weight and yet possesses excellent insulative characteristics. The core itself is too frangible to constitute a load bearing component and for that reason is combined with a skin, or reinforcement to impart at least a modicum of structural strength to the final combination.

Historically, coreboards were made in either a sandwich or a honeycomb construction. A sandwich construction comprises laminating an outer, high strength skin onto the central core. The principal drawback tothis construction is the proclivity of the skin to separate from the core when the coreboard is stressed.

The honeycomb coreboard includes, in addition, a lattice embedded within the core. The outer skins are laminated transversely onto the lattice, and the interstices of the lattice are filled with a cellular plastic core. While the honeycomb type construction is somewhat stronger than the sandwich type, the skin still separates from the core and lattice when the board is stressed. Moreover, the modest increase in strength incident to honeycomb board is not deemed suflicient to justify its increased production cost.

To obviate the drawbacks inherent to both the sandwich 3,519,523 Patented July 7, 1970 and honeycomb types of coreboard construction, a composite coreboard was devised in which the skins forming the opposed sides of the board are homogenously interconnected. This construction is disclosed in our prior US. patent, No. 3,185,611.

A composite coreboard according to our aforesaid US. Pat. No. 3,185,611, comprises a series of skin elements having a generally channel-shaped cross section which are nested together to form longitudinal cells between the spaced apart webs of the channel-like skin elements. The corresponding flanges of these nested skin elements are bonded together to form the opposed surfaces of the board, and the longitudinal cells are filled with a lightweight core material, preferably a cellular plastic.

This construction provide-s vastly improved bending strength characteristics over the historic sandwich and honeycomb constructions. In fact, tests have revealed that a coreboard constructed in this fashion has a deflection curve not only more favorable than prior known coreboard constructions blu-t also more favorable than clear, white pine lumber.

Tested to failure, the composite coreboard of the type taught by our aforesaid US. Pat. No. 3,185,611 does not fail by separation of the opposed surfaces from the core but rather does not occur until the core is crushed transversely between the opposed surfaces.

Because of the excellent strength characteristics provided by a coreboard constructed in accordance with our aforesaid Pat. No. 3,185,611, it can be used in a wide variety of applications without fear of failure. However, this favorable characteristic has led to its application as a structural substitute under loadings which tax even its fine strength. This has led to one aspect of the present invention, as will be hereinafter pointed out in detail.

As additional background information, the preferred method, as taught in our prior U.S. Pat'No. 3,264,153, for producing composite coreboard, requires inserting a core material into the longitudinal cells formed between the spaced web portions of successively nested skin elements. As shown in our prior US. Pat. No. 3,282,769, the preferred apparatus for inserting this core material utilizes a conduit means for charging the core forming material into the longitudinal cells. The core is generally a lightweight material having excellent heat and sound insulative characteristics. As is carefully delineated in our three prior patents, mentioned above, the core need not itself be a high strength material-such cellular plastics as the rigid, but frangible, foamed phenolic plastics, urethane and polystyrene being usable with excellent results. Nevertheless, the core should be sufficiently rigid to assist in maintaining the webs oriented transversely of the coreboard. With the successive longitudinal cells being completely enclosed, one must exercise great care to assure that the proper charge of core forming material is received in each cell so that as that material forms into the core it does not distort the successive webs from their preferred transverse orientation.

SUMMARY OF THE INVENTION It is therefore a primary object of the present invention to provide an improved skin element in which the septum, or web section, has inoreased columnar strength so as to increase the resistance of the coreboard against transverse crushing and thereby increase its ultimate bending strength.

It is another object of the present invention to provide an improved skin element, as above, which permits communication between adjacent longitudinal cells, at least while the core is forming, so as to preclude the imposition of any bow, or other distortion, to the improved septum which would be occasioned by faultily charging dispro- 3 portionate amounts of the core forming material into successive cells.

These and other objects which will become apparent from the following specification are accomplished by means hereinafter described and claimed.

In general, a coreboard embodying the concept of the present invention is constructed from a plurality of partially nested, channel-shaped skin elements. The skin elements are formed from a flexible material to have parallel, spaced flange portions separated by a transverse septum. The longitudinal cells between the spaced septums of partially nested successive skin elements are filled with a foamed, cellular plastic. The septums have a plurality of longitudinally spaced, lateral offsets which increase the columnar strength of the septum between the flange portions. A plurality of passages are selectively provided through the septums so as not to decrease their columnar strength and yet to provide a communication between adjacent cells.

Two alternative embodiments of the present invention are shown by way of example in the accompanying drawings and hereinafter described in detail without attempting to show all of the various forms and modifications in which the invention might be embodied; the invention being measured by the appended claims and not by the details of the specification.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view, partially broken away, of a composite coreboard employing a skin element having a septum embodying one form of the improvement disclosed herein;

FIG. 2 is an enlarged cross section taken substantially on line 22 of FIG. 1;

FIG. 3 is an enlarged cross section, depicting the septum in elevation, taken substantially on line 33 of FIG. 1;

FIG. 4 is a cross section taken substantially on line 44 of FIG. 3;

FIG. 5 is an elevation of a lateral offset taken substantially on line 55 of FIG. 2;

FIG.6 is a view similar to FIG. 3 depicting an alternative form of the improved septum;

FIG. 7 is a cross section taken substantially on line 77 of FIG. 6; and

FIG. 8 is a cross section taken substantially on line 88 of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more particularly to the drawings, the improved skin elements, indicated generally by the numeral 10, are embodied in a composite coreboard 11. Each skin element 10 has a substantially channel-shaped cross section with a web, or septum, 12 and spaced, parallel flange portions 13 and 14. Successive channel-shaped skin elements 10 are partially nested so that the flange portions 13 and 14 overlie a substantial portion, preferably about one-half, of the corresponding flange portion of each successively nested element.

The flange portion of each skin element 10 is bonded, as by adhesive 15, to the respective flange portions of the successively nested elements which they overlie. The thus bonded flange portions 13 form one surface, or skin, 16 of the board 11, and the bonded flanges 14 form a second surface, or skin, 18. By nesting and bonding the skin elements 10 together in this fashion, a series of longitudinal rectilinear cells 19 are formed. Each cell 19 is bounded on two sides by the opposed, spaced septums 12 of successively nested skin elements and on the other two sides by the opposed, spaced skins 16 and 18. The cells 19 are filled with a light weight insulative material defined as the core 20.

The composite coreboard 11 discussed to this point is fully disclosed in our aforementiQned prior U.S patents 4 and does not per se constitute a patentable aspect of our subject invention.

When coreboards utilizing constructions known prior to our concept of homogenously joining the spaced skins are subjected to bending loads, they fail in shear at the bond between the core material and the skin. The composite coreboard heretofore described will not so fail. When this board is subjected to a bending load, one of the skins is subjected to a compressive stress and the other to a tensile stress. Whereas the skin of a nonhomogenous coreboard would buckle under compressive loading and pull away from the core, with an homogenous construction the unitary connection of the skins with septums restrains the skin subjected to compression from buckling. At the same time this unitary construction causes the tensile stress in the opposite skin to be distributed into the septum. In this way the ultimate strength of the homogenous construction is greatly enhanced over the ultimate strength of the nonhomogenous prior coreboard constructions.

A close study of numerous homogenous coreboards bent to failure reveals that failure in coreboards of this construction is characterized by a bending of the web, or septum, and a concomitant crushing of the core material between the opposed skins. Further careful study reveals that the maximum load to which the septum can be subjected does not depend upon the strength of the material from which the septum is made but rather its stiffness.

And, it has been found that if the septum 12 is provided with a plurality of lateral offsets spaced longitudinally along the skin element 10 the requisite stiffness is imparted to the septum markedly to increase its ultimate columnar strength even though the skin elements are made from the flexible material noted in our prior US. patent, No. 3,185,611. In the embodiment depicted in FIGS. 1-5, the lateral offset may comprise a flap 21 struck from the septum and bent outwardly from a fold line 22 in the septum to lie angularly outwardly from the plane of the septum. With the fold line 22 extending substantially the full span of the septum between the op posed skins 16 and 18 the stiffness imparted to the septum by the laterally extending flap may be increased to the maximum.

As an example, if the coreboard depicted in FIGS. 1-5 is approximately 1 /2" in thickness, the strength thereof will be propitiously increased by the provision of flaps 21 having a width equal to approximately the span of the septum between opposite skinsi.e., one-quarter of an inchspaced longitudinally along the septum of the skin elements 10 on centers approximately one and one-third said spani.e., two inches. It will be observed that each flap 21 is arcuately rounded, as at 23 and 24, from immediately adjacent the intersection of the fold line 22 With the skins 16 and 18 to the free edge 25 which is spaced most remotely of the fold line 22. This minimizes any weakening of the septum adjacent the opposed skin surfaces.

Also advantageously, the folding of the flap 21 laterally outwardly from the septum 12 leaves a passage 26 therethrough which further serves to assure a satisfactory stiffness in the septums by assisting in the maintenance of the required transverse orientation of the septum with respect to the opposed skins 16 and 18. The passage 26 permits any excess core material in one cell to flow, or otherwise pass, into the adjacent cell during the formation of the core. As such, the material forming the core will equalize across the septums and thereby preclude the possibility of any original distortion, or bowing, of the septums which might result were a disproportionate amount of the core forming material received in any one or more of the cells. Were the septum bowed, or otherwise altered from its transverse orientation, the septum would lose its columnar resistance and fold under the eccentricity of the loading applied thereto by the skins 16 and 18 when the board 11 was bent.

A second form of lateral offset for adding stiffness to the septum is depicted in FIGS. 6-8. In this form the septum 12' or skin element is provided with a series of alternately directed crimps 28 extending transversely between the opposed skins 16' and 18'. Each crimp forms a concave depression 29 on one side of the septum and a corresponding convex ridge 30 on the opposite side. Thus, the alternate direction of the crimps presents a ridge 30 spaced medially between successive depressions 29 when the septum is viewed from the cell on either side thereof. Here too, the equalization of the core between the adjacent cells during formation of the core is achieved by the provision of passages 26 through the septum. In this form an annular aperture in the wing wall 31 between crimps 28 accomplishes the desired interconnection of cells without weakening the columnar strength of the septum provided by the crimps.

As an example, if the coreboard depicted in FIGS. 68 is approximately 1%" in thickness, the strength thereof will be propitiously increased by the provision of crimps 28 spaced longitudinally along the septum on centers approximately one-third the span of the septums between opposed skins 16 and 18'i.e., one-half inch.

It should also be noted that in either embodiment of the septum the passages 26 and 26' provide a mechanical bond between the core material in the adjacent cells so that the septum is further supported in its transverse orientation by the core itself. Although this improved columnar strength of the septum also increases the strength of the board to direct loading applied transversely of the skins, the primary benefit is the increased bending strength derived by the composite board.

It should now be apparent that a septum constructed in accordance with the present concept will tend to increase the strength of the composite coreboard and otherwise accomplish the objects of the invention.

What is claimed is:

1. A composite coreboard having a plurality of channel-shaped skin elements formed from a flexible material to have opposed, spaced, generally parallel flange portions between which a septum extends transversely, said skin elements being partially nested with the flange portions overlappingly joined and the septums on successively nested elements being spaced, a core material between the spaced septums of partially nested successive skin elements, a plurality of lateral offsets spaced longitudinally along said septums, passage means spaced longitudinally along said septums, said core material extending through said passage means, said lateral offsets extending substantially the full span of said septums between said opposed flanges.

2. A composite coreboard, as set forth in claim 1, in which the lateral offsets comprise alternatingly directed crimps in said septums and in which wing walls are provided between successive longitudinal spaced crimps and the passages extend through said wing walls.

3. A coreboard, as set forth in claim 2, in which the crimps are spaced on centers approximately one-third the span of said septums.

4. A coreboard, as set forth in claim 1, in which the lateral offsets are flaps struck from said septums, and the passages are the openings in said septums from which said flaps are struck.

5. A coreboard, as set forth in claim 4, in which the flaps have a width equal to approximately one-sixth of the span of said septums.

6. A coreboard, as set forth in claim 5, in which the flaps are spaced on centers approximately one and onethird the span of said septums.

7. A coreboard, as set forth in claim 4, in which the flaps extend laterally of said septums from a transverse fold line in said septums and in which the flaps are rounded from the intersection of said fold line with the opposed flanges away from the flange sections.

References Cited UNITED STATES PATENTS 3,185,611 5/1965 Rodman et al. 161-104 XR 1,915,611 6/1933 Miller 16l-1l1 XR 3,446,692 5/1969 Turnbull 161-69 3,231,452 1/1966 Thomas 161-36 XR 2,733,177 1/1956 Meyer 161111 XR 2,836,863 6/1958 Denker l61111 XR 3,443,349 5/1969 Mahle 161-111 XR PHILIP DIER, Primary Examiner US. Cl. X.R. 

